Scaffold systems are often formed from steel tubes joined together by means of coupling members.
In the scaffolding industry, the possible benefits of plastic tubing over the present steel tube systems have long been known. These benefits include the reduced weight and electrical insulation afforded by the plastic tubing. However, plastic tubing scaffold systems have not been accepted generally.
Coupling members are used with scaffolding tubing in the construction of a scaffold structure. Coupling arrangements as taught in U.S. Pat. Nos. 4,044,523 of Layher, 4,493,578 of D'Alessio, 4,587,786 of Woods and 4,840,513 of Hackett, are exemplary of disc couplers known in the art of scaffold systems. The disc coupling members comprise a single disc with a plurality of apertures formed in the disc to allow the locking of adapters to the disc. The disc of such a coupling member bears the horizontal tensile loads, vertical compressive and shearing loads as well as the bending loads imparted by the horizontal and diagonal members of the scaffold structure. Horizontal tensile loads are supported most directly by the annulus of material exterior to the apertures in the disc. This same annulus and the points of contact between the various parts of the coupler and adapter are responsible for much of the bending strength and stiffness of the coupling.